Input device with an array of force sensors in a film layer structure with improved durability and simplified production

ABSTRACT

The present disclosure relates to an input device comprising a flat panel defining an array of control surfaces, a support disposed on a side of the panel, and a substantially flat film layer placed between the panel and the support defining an array of capacitive sensors, wherein each control surfaces comprises backlightable luminous surfaces and are disposed on a surface of the panel facing towards an operator, wherein each capacitive sensor forms a measuring capacitance assigned to one control surface, wherein the panel has a light-conducting layer covering the luminous surfaces, wherein a lighting means is provided for each control surface for backlighting the associated luminous surface of the control surface while transmitting light through the light-conducting layer, wherein the support forms a web which protrudes towards the panel and is connected to the panel in order to fix the film layer structure between the panel and the support.

This application claims priority to the German Application No. 10 2018110 033.7, filed Apr. 26, 2018, now pending, the contents of which arehereby incorporated by reference.

The present disclosure relates to an input device comprising a flatpanel defining an array of control surfaces, and a film layer structure,which defines an array of capacitive sensors, e.g. capacitive forcesensors, and a support, wherein the control surfaces are disposed on asurface of the panel facing towards the operator, and the support isdisposed on a side of the panel facing away from the operator.Generically, one of the capacitive sensors, respectively, forms onemeasuring capacitance assigned to one of the control surfaces. Thecontrol surface in each case includes a luminous surface. On the side ofthe support, at least one lighting means is provided for each controlsurface, for backlighting these luminous surfaces.

This type of input devices, depending on the design of the capacitivesensor, for example, focuses on the exclusive detection of touch, or onthe detection of the actuating force exerted in the process, by thecapacitive sensors being configured as force sensors. There is in factan increasing demand for such input devices in which the operatorreceives a haptic feedback when the operator makes an input on the inputsurface. In order to better distinguish random contacts on the inputsurface from intended actuation, and in order to be able to provide theoperator, who is used to traditional mechanical operating elements, witha similar haptic feedback, such input devices were developed whichpermit an actuating force measurement to be able to generate a hapticfeedback depending on the measured actuating force.

In the case of input devices with an array of operating surfaces, i.e.with several operating surfaces accommodated in an extended inputsurface, an array of several force sensors is provided for “spatialresolution”. In this case, a force sensor is assigned to each operatingsurface in order to be able to assign a switching function to anactuation of the individual operating surface, hereinafter also referredto as control surface, e.g. when a measured minimum actuating force ofthe actuation is exceeded. Compared to piezo-electric sensors, forinstance, capacitive sensors are inexpensive, and a force measurement,but also the mere touch detection, with this type of sensor can berealized in a space-saving manner by using a film layer structure.

One drawback with this type of capacitive sensors with a film layerstructure is that the production makes great demands with respect to thepositioning accuracy and that the permanent maintenance of the positionof the film layer structure has to be ensured. On the one hand, this isdue to the capacitive detection, which reacts sensitively toinaccuracies and production spread. This applies all the more if abacklighting of parts of the control surfaces is to be realized at thesame time, which creates additional problems because of the backlightingbeing intended to be as uniform as possible. In addition to the requiredhighly precise assembly positioning, the permanent retention of thisoriginal positioning has to be ensured under the adverse ambientconditions prevailing in the vehicle. At the time the present disclosurewas made, the problems concerning durability and thus, inter alia,permanent reproducibility of capacitive detection were not solved.

Against this background, there was a demand for a solution for an inputdevice with an array of control surfaces and an associated array ofcapacitive sensors accommodated in a film layer structure, which isimproved with regard to durability and production, and which is, inparticular, inexpensive to produce. This object is achieved with aninput device according to claim 1. An equally advantageous use and aproduction method are each the subject matter of the independent claims.Advantageous embodiments are in each case the subject matter of thedependent claims. It must be noted that the features cited individuallyin the claims can be combined with each other in any technologicallymeaningful manner and represent other embodiments of the presentdisclosure. The description, in particular in connection with thefigures, additionally characterizes and specifies the presentdisclosure.

The present disclosure relates to an input device comprising a flatpanel defining an array of control surfaces, a support disposed on aside of the panel facing away from the operator, and a substantiallyflat film layer structure, which is disposed between the panel and thesupport and which defines an array of capacitive sensors. For example,the panel is configured to be elastically more yielding compared withthe support and/or movably mounted with respect to the support.According to the present disclosure, the control surfaces are disposedon a surface of the panel facing towards the operator, i.e. disposed soas to be visible from the point of view of the operator, whereas,according to the present disclosure, the support is disposed on a sideof the panel facing away from the operator, i.e. underneath the panelfrom the point of view of the operator. The term “control surface” is tobe interpreted broadly, and despite the designation referring to anactuation, a mere touch without the influence of an actuating force isalso to be understood to be an actuation in the sense of the presentdisclosure. According to the present disclosure, the control surfaceseach comprise backlightable luminous surfaces and the control surfacesare disposed on a surface of the panel facing towards the operator.According to the present disclosure, the panel, on the side facingtowards the support, has a light-conducting layer of transparent oftranslucent material, which covers the luminous surfaces in a connectingmanner and which defines, in particular, a surface facing towards theoperator. For example, the light-conducting layer is integrally formedand is in touching contact with all luminous surfaces.

According to the present disclosure, each of the capacitive sensors isprovided to respectively form a measuring capacitance respectivelyassigned to one of the several control surfaces. According to thepresent disclosure, the capacitive sensor has in each case at least onefirst electrode which is more closely adjacent to the panel, and is thusdesigned, for example, to capacitively detect a touch on the associatedcontrol surface. Preferably, the capacitive sensor is in each casedesigned as a capacitive force sensor, and further includes at least onesecond electrode, which is more closely adjacent to the support, forforming the measuring capacitance between the support and the panel.

For example, the mode of operation of the capacitive sensor, which ispreferably configured as a capacitive force sensor, is as follows. Whenan actuating force acts on the respective control surface of the panel,this results in the first and second electrode converging and thus in achange in the measuring capacitance, which is detected by an evaluationunit and which, when a predetermined minimum change is exceeded, causesa switching state of a unit to be controlled with the input device tochange. Preferably, the input device also has an actuating element, alsoreferred to as actuator, for generating a haptic feedback, which isactivated at the same time as or subsequent to the assignation of theswitching state change by the evaluation unit in order to produce avibration or impact-like positional change of the input device forgenerating a haptic feedback.

According to the present disclosure, each of the capacitive sensors isformed by a substantially flat film layer structure common to allcapacitive sensors. A film layer structure in the sense of the presentdisclosure is understood to be, for example, a single-layer film with aunilateral coating. In the case of the capacitive sensors being designedas pure touch sensors, for example, the film layer structure has a filmwith a unilaterally applied, only partial, metallic coating, whereinthese partial coatings, which are electrically insulated from oneanother, each define an electrode for forming a measuring capacitance.In the case of the capacitive sensors being designed as capacitive forcesensors, for example, the film layer structure, for each force sensor,in each case has at least one first electrode which is more closelyadjacent to the panel, and at least one second electrode, which is moreclosely adjacent to the support, for forming the measuring capacitance.This is not to exclude the possibility that at least one electrode ofseveral or all force sensors is configured as a common electrode to therespective or all force sensors.

Preferably, the electrode or the electrodes are formed from a conductivematerial, for example as a metallic coating of one of the film layers ofthe film layer structure. For example, the first and second electrodesof the capacitive sensor configured as a force sensor are spaced apartfrom each other by an elastically yielding intermediate layer, which isintegrated into the film layer structure and passes through the filmlayer structure over the entire surface or forms cushions in some areas,or by a distance layer, which yields comparatively little and whichdefines a hollow volume in each case between the first electrode and thesecond electrode.

According to the present disclosure, on the side of the support, whichpreferably consists of an opaque material, preferably opaquethermoplastic material, at least one lighting means, e.g. alight-emitting diode, preferably with an SMD design, is provided foreach control surface, for backlighting the control surface andtransmitting light through the light-conducting layer, and which isassigned to the control surface. Backlighting serves for making theluminous surface associated with the respective control surface moreeasily recognizable or visible to an operator looking at the controlsurface, or for displaying by means of the luminous surface theswitching functionality connected with the respective control surface,for example by a symbol, which is applied to the luminous surface orrepresented by the shaping of the luminous surface, being backlit.

According to the present disclosure, the support forms one or more webs,which protrude towards the panel and are connected in each casenon-positively and/or by substance-to-substance connection, preferablyby means of their ends pointing away from the support, to thelight-conducting layer, in order to fix the film layer structure betweenthe panel and the support. As a result, a stability-providing connectionbetween the panel and the support is obtained, which is provided not onthe peripherally extending edge of the support and/or the panel, butrather within the flat extent of the panel and the support. It is alsoensured that the film layer structure is fixed, e.g. clamped, betweenthe support and the panel in a more permanent manner and without anydanger of a subsequent positional change with an associated effect onthe measuring capacitances.

Preferably, it is provided that the web or webs are disposed in such away that the end thereof pointing away from the support is disposedbetween the luminous surfaces. As a result, the web provides for a lightshielding effect between the luminous surfaces. The webs prevent“crosstalk” of the backlight from one control surface to another controlsurface in order thus to improve visual appearance, but also to avoidoperating errors, particularly if certain switching states of theswitching function associated with the control surface are to be madevisible by the kind of backlighting that are associated with therespective control surface. For example, the web extends parallel to themain emission direction of the lighting means.

According to a preferred embodiment, at least the webs of the support,preferably the entire support, are made from a thermoplastic material.In this case, the light-conducting layer is also made from athermoplastic material. In this configuration, the web, and thus thesupport, is respectively welded to the light-conducting layer. A weldedconnection between the support and the light-conducting layer isobtained by ultrasonic welding.

Preferably, the panel is formed by a decorative film that is back-moldedwith a translucent or transparent thermoplastic material for forming thelight-conducting layer.

According to a preferred embodiment, the web or webs are formed so as toreach through the film layer structure, wherein the web, morepreferably, is disposed so as to protrude beyond the film layerstructure in the direction of the panel in each case.

Preferably, the film layer structure has at least one opaque layer andone or several through-holes for the passage of light from therespective lighting means to the light-conducting layer of the panel. Inthis case, the web is disposed so as to reach through one through-hole,respectively, of the film layer structure.

Furthermore, the present disclosure relates to the use of the inputdevice in one of its above-described embodiments in a motor vehicle.

The present disclosure further relates to a production method for aninput device with the steps described below.

In a step of providing, a flat panel defining an array of controlsurfaces with a light-conducting layer is provided, wherein the controlsurfaces each comprise backlightable luminous surfaces and the controlsurfaces are disposed on a surface of the panel facing towards theoperator. In this case, the light-conducting layer, which covers theluminous surfaces and preferably forms a surface facing towards thesupport, is provided on the side of the panel facing away from theoperator. In another step of providing, a support is provided, wherein,on the side of the support, at least one lighting means is provided foreach control surface, for backlighting the associated luminous surfaceof the control surface while transmitting light through thelight-conducting layer. The support forms one or more webs protrudingtowards the panel.

In a step of arranging, a substantially flat film layer structure isdisposed between the panel and the support, wherein the film layerstructure defines an array of capacitive sensors and each of thecapacitive sensors forms a measuring capacitance assigned to one of thecontrol surfaces.

In a subsequent attaching step, the panel and the support are fastenedby the web or webs being connected, positively and/or bysubstance-to-substance connection, to the panel, particularly to thelight-conducting layer, in order to fix the film layer structure betweenthe panel and the support. As a result, a stability-providing connectionbetween the panel and the support is obtained, which is provided not onthe peripherally extending edge of the combined assembly of the paneland the support, but rather within the flat extent of the panel and thesupport. It is also ensured that the film layer structure is fixed, e.g.clamped, between the support and the panel in a more permanent mannerand without any danger of a subsequent positional change with anassociated effect on the measuring capacitances.

According to a preferred variant of the production method according tothe present disclosure, there are provided a support production step,which precedes the step of providing and in which the support is madefrom a thermoplastic material, and a panel production step, whichprecedes the step of providing and in which the panel is made byback-molding a decorative film with a translucent or transparentthermoplastic material while producing the light-conducting layer.

In the fastening step, the panel and the support are fastened by weldingthe webs to the light-conducting layer. Preferably, the welding iscarried out using ultrasound, for example by placing an ultrasoundwelding head on the support on the surface facing away from the paneland coupling ultrasound into the support.

The present disclosure is explained further with reference to thefollowing Figures. The Figures are to be understood only as examples andmerely represent a preferred embodiment. In the Figures:

FIG. 1 shows a sectional view through an embodiment of the input deviceaccording to the present disclosure;

FIG. 2 shows an associated detailed view;

FIG. 3 shows a top view of the support of the embodiment of the inputdevice according to the present disclosure shown in FIG. 1, with thefilm layer structure 4 disposed thereon.

FIG. 1 shows an embodiment of the input device 1 according to thepresent disclosure. The input device 1 has an array of control surfaces20 a, 20 b, which is formed on a surface, which faces towards theoperator, of a flat panel 2 made from a decorative layer 9 and alight-conducting layer 6 which, viewed from the operator's point ofview, is situated thereunder. The transparent layer 6 is formed from atranslucent or transparent thermoplastic material and, by back-moldingthe decorative layer 9, is applied thereto substantially across theentire surface and connected therewith. In order to be found more easilyor for displaying a switching state if required, the control surfaces 20a, 20 b have selectively backlightable luminous surfaces 10 a, 10 b. Forindicating the associated switching function, which is to be activatedby the actuation of the control surface 20 a, 20 b, correspondingsymbols are displayed by means of the luminous surfaces 10 a, 10 b.

The input device 1 further has a support 3 made from an opaquethermoplastic material, which is disposed on the far side of the panel2. A film layer structure 4, which defines an array of capacitive forcesensors 21 a, 21 b, is disposed between the panel 2 and the support 3,wherein exactly one of the capacitive force sensors 21 a, 21 b isassigned to each control surface 20 a, 20 b. Each of the force sensors21 a, 21 b is provided for forming, by means of a evaluation unit thatis not shown, a measuring capacitance between the panel 2 and thesupport 3, which is assigned to one of the control surfaces 20 a, 20 b.The film layer structure 4, for each force sensor 21, 21 b, has at leastone first electrode 11 a, 11 b which is more closely adjacent to thepanel 2, and at least one second electrode 12 a, 12 b, which is moreclosely adjacent to the support 3, for forming the above-mentionedmeasuring capacitance. As FIG. 2 shows in detail, the first electrodes11 a, 11 b are formed as a metallic coating of the surface of a firstfilm of the film layer structure 4 facing towards the panel 2, whereasthe second electrodes 12 a, 12 b are formed as a metallic coating of thesurface of a second film of the film layer structure 4 facing towardsthe support 3. The film layer structure 4 may have further films orfilm-like layers. Alternatively, the film layer structure 4 may definean array of capacitive touch sensors. For example, this is a filmpartially metal-coated on one side, wherein the metallic layers areelectrically insulated from one another and serve as electrodes forgenerating a measuring capacitance. In the embodiment shown in FIG. 1,the film layer structure has an elastically deformable distance layer 9,which is provided between the first film supporting the first electrodes12 a, 12 b and the second film supporting the second electrodes 12 a, 12b, in order to permit an elastic deformation and thus a reversibleconvergence of the associated electrode pairs 11 a, 12 a or 11 b, 12 b,and thus a detectable change in the associated measuring capacitance ofthe capacitive force sensors 21 a, 21 b, when an actuating force acts onthe control surfaces 20 a, 20 b. On the side of the support 3, onelighting means 5 a, 5 b is respectively provided for each controlsurface 20 a, 20 b, for backlighting the associated luminous surface 10a, 10 b associated with the respective control surface 20 a, 20 b, whiletransmitting light through a though-hole D provided in the film layerstructure 4 and the light-conducting layer 6. The lighting means 5 a, 5b are configured in an SMD design and disposed on a circuit board, whichis not shown in more detail, on the support 3. A web 7 rises frombetween the lighting means 5 a, 5 b. FIG. 3 shows an associated top viewof the support 3, which illustrates the structure, from the side of theoperator, with the film layer structure 4 disposed on the support 3.

The web 7 reaches through the through-hole D in the film layer structure4 and, at the end 8 thereof that faces away from the support and isshown in FIG. 1, is connected by substance-to-substance connection tothe light-conducting layer 6 of the panel 2 through ultrasonic welding,in order to fix, on the one hand, the film layer structure 4 between thesupport 3 and the panel 2 in a clamping manner and, on the other hand,fix the support 3 to the panel 2. The web 7 further reduces the passageof light from one luminous surface 10 a to an adjacent luminous surface10 b in order to prevent an undesirable light transfer of the lightsource 5 b to the respective other control surface 20 a or 20 b.

1. An input device comprising: a flat panel defining an array of controlsurfaces: a support disposed on a side of the panel facing away from theoperator; and a substantially flat film layer structure disposed betweenthe panel and the support and which defines an array of capacitivesensors, wherein the control surfaces each comprise backlightableluminous surfaces and the control surfaces are disposed on a surface ofthe panel facing towards an operator; wherein each of the capacitivesensors forms a measuring capacitance assigned to one of the controlsurfaces, wherein the panel, on the side facing towards the support,includes a light-conducting layer covering at least the luminoussurfaces in a connecting manner, wherein, on the side of the support, atleast one lighting means is provided for each control surface forbacklighting the associated luminous surface of the control surfacewhile transmitting light through the light-conducting layer; wherein thesupport forms at least one web, which protrudes towards the panel and isconnected to the panel in order to fix the film layer structure betweenthe panel and the support.
 2. The input device of claim 1, wherein theweb is configured such that the end thereof pointing away from thesupport is disposed between the luminous surfaces.
 3. The input deviceof claim 1, wherein the web is made from a thermoplastic material, thelight-conducting layer is made from a thermoplastic material, and thesupport is welded to the panel.
 4. The input device of claim 3, whereinthe panel has a decorative film that is back-molded with a translucentor transparent thermoplastic material for forming the light-conductinglayer.
 5. The input device of claim 1, wherein the web is formed so asto reach through the film layer structure protruding beyond the filmlayer structure in the direction of the panel.
 6. The input device ofclaim 1, wherein the film layer structure has at least one opaque layerand has one or several through-holes for the passage of light from therespective lighting means to the light-conducting layer.
 7. The inputdevice of claim 6, wherein the web is disposed so as to reach throughone through-hole, respectively, of the film layer structure.
 8. Theinput device of claim 1, configured for use in a motor vehicle.
 9. Amethod for producing an input device comprising the following steps:providing a flat panel defining an array of control surfaces, whereinthe control surfaces each comprise backlightable luminous surfaces andthe control surfaces are disposed on a surface of the panel facingtowards an operator, wherein a light-conducting layer covering theluminous surfaces in a connecting manner is provided on the side of thepanel facing away from the operator; providing a support, wherein, on aside of the support, at least one lighting means is provided for eachcontrol surface for backlighting the associated luminous surface of thecontrol surface while transmitting light through the light-conductinglayer, and the support forms at least one web, which protrudes towardsthe panel; disposing a substantially flat film layer structure betweenthe panel and the support, wherein the film layer structure defines anarray of capacitive sensors, wherein each of the capacitive sensorsforms a measuring capacitance assigned to one of the control surfaces;and fastening the panel and the support, by the web being connected, tothe panel in order to fix the film layer structure between the panel andthe support.
 10. The method of claim 9, further comprising a supportproduction step, in which the support is made from a thermoplasticmaterial, and a panel production step, in which the panel is made byback-molding a decorative film with a translucent or transparentthermoplastic material while forming the light-conducting layer, and,when fastening the panel and the support, the web is welded to thelight-conducting layer.